A device for use in a pressure microphone or in connection with a pressure microphone comprising a microphone housing and an oscillating element mounted in or on said housing, a membrane, which is in principle only sensitive to a sound field on one side, the second side forming part of a closed cavity in the microphone housing, said cavity representing a first acoustic capacitance and being connected to the ambient atmosphere through a narrow pressure equalizing channel representing a first acoustic resistance, said device comprising an additional cavity representing an additional acoustic capacitance and an additional pressure equalizing channel located in series therewith and representing an additional acoustic resistance. The second capacitance and the second resistance are located in series with the capacitance and the resistance, respectively, of the first cavity and the first channel in such a manner that the pressure equalization of the microphone is also effected through the additional pressure equalizing channel and the additional cavity.